40 COPD patients (21 smokers and 19 never smokers) and 28 healthy never smokers were included in the present study. Information about respiratory symptoms and comorbidities were collected. Subjects underwent pulmonary function tests and COPD was defined according to Global Initiative for Chronic Obstructive lung Disease spirometric criteria. Induced sputum was collected to determine total and differential inflammatory cells counts as well as inflammatory mediators (Interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α)). The Mann-Whitney U and the χ2 tests were used for results comparisons. Correlations between symptoms, spirometric parameters, cytokines levels, inflammatory cells and risk factors of COPD were examined with Spearman's rank correlation test.
